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Intermittent fasting is arguably the biggest diet trend right now, and if your clients ask you about it you need to be prepared:
How do you do intermittent fasting?
Is it right for me?
Will I lose weight?
Can I eat whatever I want?
Intermittent fasting is a style of eating rather than a restrictive diet, which is a major appeal for a lot of people looking to trim down. But this doesn't mean it works for everyone. Indeed, weight loss results from any diet are most often due to the severe reduction of calories. The ISSA doesn't necessarily recommend intermittent fasting, but instead aims to make sure you're up to date on fitness and nutrition trends to stay relevant with clients.
Intermittent fasting is often thought of as a diet, but it's actually a style or pattern of eating, not a diet. What differentiates it from a diet is that fasting does not have anything to do with what you eat, rather when you eat. This is not to say that clients should go ahead and start without consulting their physician. You should always encourage them to talk to their doctor before making any major changes in their eating habits.
It is a simple pattern of eating that shifts between designated periods of fasting—not eating at all or severely restricting calorie intake—and periods of eating healthfully. Exactly when and for how long the fasting periods last depends on individual choice.
A lot of research has been done to determine if intermittent fasting is safe, effective for weight loss, and beneficial for overall health. The results indicate that this style of eating can help with weight loss and can provide a number of health benefits, while risks are seemingly low.
The number one reason people choose to fast intermittently is to lose weight. And the good news is that it's effective. If you don't go overboard during eating times, you should lose weight. The main reason for this is that an intermittent fast reduces your calorie intake overall. There are some other hormonal and metabolic factors at work that can up weight loss, but generally it is the reduced calories that make intermittent fasting work.
As a trainer you know that losing weight is not always a simple matter of watching the number on the scale decrease. Losing weight may result from fat loss, muscle loss, or both. Of course, what we want is fat loss, but that doesn't always happen with simple calorie or food restriction.
A benefit of intermittent fasting is that it seems to promote fat loss, not just weight loss. Fasting triggers human growth hormone, which is beneficial for fat loss and muscle gain. Fasting also increases insulin sensitivity, another hormone change that results in loss of fat.
One of the best things about this pattern of eating is that it isn't actually a diet. Counting calories, restricting certain foods, sticking with a paleo or plant-based diet dictate what you can eat, but intermittent fasting only dictates whenyou can eat.
This is an approach to weight loss that is much simpler. You can technically eat whatever you want. The only stipulation is that you restrict when you eat. Of course if you decide to use your eating times to binge and eat nothing but junk, weight loss probably won't happen.
Weight and fat loss are important benefits of this eating pattern, but there are others:
Lowered blood sugar and reduced insulin resistance
Reduced cancer risk
Improved side effects from chemotherapy
Lower LDL cholesterol and blood triglycerides
Reduced risk of heart disease
Improved brain health
To learn more about how fasting before a workout affects weight loss, check out this fasted exercise post on the ISSA blog.
There is no single approach to intermittent fasting that is right for everyone. It's a choice based on personal preference and how likely an individual is to stick with it for the long-term. If your client is interested in trying intermittent fasting, lay out the options and help her choose.
This is kind of an intense way to practice intermittent fasting. It involves a complete fast—no eating at all—for 24-hour periods. It shouldn't be done for more than two days per week, and there are some issues your client may face.
Not eating for 24 hours may be difficult to sustain. There can also be some health risks and certainly impacts on mood and well-being. Being unable to take in any calories at all for a full day and night can also interfere with workouts and training.
A more popular approach is to fast for 16 hours every day. Most people who practice the 16/8 fast skip breakfast. A typical way to do this is to skip breakfast and to eat lunch at 1 pm and dinner at 8 pm. The fast lasts from 9:00 each night to 1:00 the following day.
A modified type of intermittent fasting is also known as the 5:2 diet. You eat normally five days a week, and restrict calories on the other two days. Women are supposed to eat just 500 calories on fast days, while men should stick with 600. The fast days are not consecutive.
One of the good things about intermittent fasting is that it doesn't come with any hard and fast rules. You can vary the general idea and come up with eating plans that work best for you or your client. These are some other popular variations:
12/12 fast. An easier version of 16/8, this means fasting for just 12 hours, like 7 pm to 7 am. It may not have as many benefits as the stricter 16-hour fast, but it can be a good way to ease into fasting.
Fasting every other day. This should not be a complete fast, but a calorie restriction—500 to 600 calories consumed. Alternate fast days with no-restriction days.
The warrior diet. This is a diet that does include food restrictions, a variation of paleo eating. But, the fasting part of the diet involves eating only a little bit of fruits and vegetables for most of the day and then enjoying a feast or large meal during a four-hour window in the evening.
Skipping meals. One of the most convenient ways to try fasting is to simply let your own schedule, mood, and other factors dictate when you do it. Skip a meal here and there when it suits you.
There are many variables to consider when it comes to creating a beneficial dietary outline for your clients. Our Nutrition Specialist course will help you better understand nutrient timing, hormonal changes, psychological factors, etc., so you can educate your clients and help them make the right choice for them. Of course, this includes weighing the pros and cons of certain diets.
A lot of the evidence from research into fasting diets proves that this is an overwhelmingly beneficial way to eat. However, that doesn't mean there are no risks. Before your clients try fasting, make sure you go over any potential pitfalls and help them select a style of intermittent fasting with the lowest risks.
Unfortunately a lot of research is done mostly with male participants. There have been some studies of intermittent fasting, though, that compare effects for women and men. And the results show it's not all rainbows and sunshine for women.
In one study, men who fasted had better insulin sensitivity, but the women involved had decreased blood sugar control. There is also plenty of anecdotal evidence that women may experience missed menstrual cycles. For your female clients, have them ask their doctors about fasting and if given the go-ahead, help them ease into it.
Learn more about women and intermittent fasting by checking out this in-depth post on the ISSA blog.
Naturally, a major side effect of fasting is that you'll feel hungry. Some people cope better with this than others. Fasting can make you feel weak; it can put you in a really sour mood; and it can even decrease your cognitive performance, making it difficult to think, make decisions, or just do your work.
Those who don't respond too well to a fasting period may be at a greater risk of overdoing it during time periods with no restrictions. If your client struggles to reign in the urge to eat a whole pizza, a two-liter of soda, and several meatball subs during the eight hour window, this might not be the right diet for him.
So should you encourage your client to try intermittent fasting? If he or she has weight loss goals and is struggling to meet them, it's a valid possibility. Most of all, though, you are there to provide good information to help a client make the right personal choice.
Intermittent fasting shows great promise, both for weight loss and for overall good health. Just remember that it's not for everyone, and that the most important thing for your clients to remember is to eat a healthy, well-balanced diet that avoids junk and empty calories, whether they choose to fast or not.
If you want to learn more about nutrition, weight loss, and fitness check out the ISSA's comprehensive course for nutrition specialists.
Hartman, M.L., Veldhuis, J.D., Johnson, M.L., Lee, M.M., Alberti, K.G., Samoijik, E., Thorner, M.O. (1992) Augmented Growth Hormone (GH) Secretory Burst Frequency and Amplitude Mediate Enhanced GH Secretion During a Two-Day Fast in Normal Men. J. Clin. Endocrinol. Metab. 74 (4) 756-65
Varady, K.A., Hellerstein, M.K. (2007). Alternate-Day Fasting and Chronic Disease Prevention: A Review of Human and Animal Trials. American Journal of Clinical Nutrition. 86 (1) 7-13
Heilbronn, L.K., Civitarese, A.E., Bogacka, I., Smith, S.R., Hulver, M., Ravussin, E. (2005). Glucose Tolerance and Skeletal Muscle Gene Expression in Response to Alternate Day Fasting. Obesity Research. 13 (3) 574-81